Lecture 6 - Exam 3: Chromatin Flashcards
What is Chromatin?
A mix of DNA and proteins (histones).
The nucleus of each cell is around ________ inches in diameter… and you can fit ____ feet of DNA in each nucleus.
0.002 ; 6
What do histones do?
Condense/organize DNA
Describe the different stages of chromatin compaction.
- DNA double helix
- DNA wrapped around histones (nucleosomes). Less condensed chromatin.
- Chromatin fiber of packed nucleosomes. Highly condensed chromatin.
- Further condensation of chromatin fibers.
- Chromosomes
Chromatin becomes highly condensed during ______ to form the compact _________.
mitosis ; metaphase chromosomes.
What is the process of karyotyping?
- From blood sample, white cells are being isolated.
- Induction of mitosis with specific chemical reagents.
- Harvest chromosomes
- Analysis
Karyotypes are particularly important for what?
Karyotypes are particularly important during pregnancy, to predict potential abnormalities in the fetus.
Describe interphase chromatin. [what does it look like and what does the position of chromatin tell us]
Interphase chromatin looks uniformly distributed, but chromosomes actually occupy distinct regions of the nucleus.
Their positions are organized so that the transcriptional activities of genes are correlated with their position in the nucleus.
What is Euchromatin?
Less condensed and can be transcribed.
What is Heterochromatin?
Highly condensed and is typically not transcribed.
Individual chromosomes are arranged in specific areas of the nucleus called..?
And their DNA generally doesn’t…?
A chromosome territory ;
Interact among chromosomes.
[Distribution of transcriptionally active and inactive chromatin]
The genome is divided into a series of what? What does this allow?
What is this important for?
The genome is divided into a series of looped domains which allow the DNA domains within a loop to interact with one another but infrequently with the domains of other loops! Important for transcriptional control.**
What are looped domains of transcriptionally inactive heterochromatin generally associated with?
Either the lamina (using lamina-associated domains or LADs*) or the nucleolus (using nucleolus associated domains or NADs).
Transcriptionally active domains (euchromatin) are localized where?
To the interior of the nucleus
Chromatin within the nucleus is organized into looped domains formed by the interaction of..?
Enhancers are restricted to interacting with..?
The CTCF transcription factor and Cohesin ;
Promoters in the same domain
